trailer in my living room (must read)

Hi all.
I wonder if anybody has seen this before.
When I was house shopping, I specifically gave the realtor one requirement: no trailers/doublewides/modular homes.

But the house I ultimately went for was built out from a singlewide trailer. The inspector who looked at my house when I bought it (several years ago) assured me that, while parts of the trailer remained, the house was entirely stick built with a foundation, and simply had been built "around a trailer" on one side. I don't know that much about construction, so I never bothered with it until I finally got sick of my low ceiling on the one side of the house. I called in some contractors to look at it and they said that I actually had a trailer roof in my attic below the rafters! Because of price constraints, I had them take out the middle 1/3 of the ceiling (the living room where it was bugging me most), and then cut through the trialer roof and remove it. Then they were able to put in a standard 8' drywall ceiling This pleased me much.

But of course, now on either side of my bright, spacious living room are two low ceilings. I can't afford to have those guys do the work again (tripling the total cost), but I think I've learned a bit by watching the progress of the work they did. Again, I know very little about construction, but I'm prepared to spend a little on the equipment and materials and try to do it myself.

Please tell me if this sounds right:

0. take down the light fixtures. (afterthought)
1. remove the cheap trailer ceiling and the wood frame behind it.
2. saw through the metal roof, cut it into manageable chunks, and remove it.
3. go around the perimeter and attach a new 2x4 pieces to cap board that runs along the top of each wall stud to make the 1-foot plus connection from the old ceiling line to the rafters (the part I'm least sure about, how to connect them stably).
4. put in insulation on the rafters (there was none there before, just trailer roof visible to the eye in the attic).
5. have a drywall contractor put up the new ceiling (I wouldn't even think of attempting that). paint it.
6. put up the drywall wall extensions and ceiling trim.
7. reattach the lights.

Have I oversimplified, left anything out, or otherwise revealed that I have no business doing this project on my own?